An Experimental Study of Trace Element Partitioning between Peridotite Minerals and Alkaline Basaltic Melts at 1250°C and 1 GPa: Crystal and Melt Composition Impacts on Partition Coefficients
Notice bibliographique
Résumé
Abstract Peridotite–magma interaction is important in establishing magma pathways through the mantle and in metasomatism of the lithospheric mantle. Reactions that consume orthopyroxene and produce olivine and clinopyroxene are of particular interest because these reactions should lead to a redistribution of trace elements between the solid and melt phases at equilibrium. This study examines interaction of a silica-undersaturated alkaline basalt (basanite) with a range of peridotite compositions from dunite, through harzburgite to wehrlite at 1250°C and 1 GPa. Our experiments used the natural concentration of trace elements in the starting materials which allowed us to measure mineral—olivine partition coefficients for Rb, Ca, Co, Sr, Sc, Ct, Y, Ti, V and Zr. For orthopyroxene—and clinopyroxene—melt we additionally measured partitioning of Cs, Ba, all rare earth elements (REE; except Pm), Hf, Th, U, Nb and Ta. We show that there are subtle variations in the partition coefficients, particularly of the REEs that are related to the bulk composition of the system. We also show that with the exception of cations that can have multiple valence states, e.g. vanadium, the lattice strain model and in particular the double fit routine gives excellent agreement between the calculated and experimentally determined partition coefficients. The double fit model allows us to examine the effect of mineral composition on partitioning such that we can show preference of trace elements for the M1 and M2 sites in the pyroxenes. Although our results are similar to those of previous studies, there are two main differences: first we have a complete set of partition coefficients for every trace element that is measurable by LA-ICPMS in our starting material, where previous studies may be missing one or more elements in particular one or more of the middle REE in the pyroxenes Second, we show that although partition coefficients for trace elements in orthopyroxene are comparable between this and previous studies, the REE in clinopyroxene are typically a factor of 2–3 lower in this study. We also note that are correlations between partition coefficient and the composition of olivine, orthopyroxene, clinopyroxene and glass (melt). The relation of partitioning to melt composition suggests that some further development of the lattice strain model is needed. Finally, we show that there is agreement between our measured partition coefficients and those predicted from parameterized models of clinopyroxene–melt partitioning, however, there are unresolved differences that may result from differences in the substitution mechanisms of trace elements in M1 vs. M2 sites in clinopyroxene that are in part related to the composition of the coexisting melt.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».